Search results

I recon I caught it quickly…it was on the ramp over winter as I chased down some issues!

The oil pump gear had failed on the primary shaft so no oil was getting round.

Quick update. I’ve had a detailed look at the crankshaft and main bearings. Looks like cylinder 4 was the worst with the main bearings showing some damage - the actual crank looks to be fine (will measure it). Cylinder 3 main bearings look like they have had some wear but nothing on the scale of...

I’m splitting the case and taking it back to a full rebuild. Will be checking tolerances on every bearing, lobe, moving part etc. Usefully I have many spare parts from a donor engine so will be replacing any damaged parts.

We have a smoking gun…the oil pump gear on the primary shaft had a rapid unscheduled disassembly. That would have led to oil starvation and the piston gouging. I’m going to look at the oil pump to check it is functioning properly - in case somehow that has failed causing the gear to fail...

Sorry, to be clear when I removed the block, the conrods have some side to side motion when they are on the crankshaft - not much, just a bit but certainly a lot more than 1 and 2. I think it’s probably within tolerance (the manual allows for a bit of movement). I’m going to split the case and...

thanks, I wouldn’t say that it’s ever been run super hot without airflow. I’ve been running it on post rebuild and chasing low compression/cold pipes for quite a while. It’s frustrating as I don’t feel like I have a smoking gun on this yet.

So, here are all 4 pistons. They were clean when they went in but 3 & 4 are really covered in soot. I mixed the plugs up so I can’t tell but a couple are also quite covered in soot. That suggests the mixture was too rich I guess. Would it really have caused that much damage? Edit: also...

thanks, liners were lubed/oiled up - by hand on assembly. I’m interested in the lean running idea, would this leave a lot of soot on the surface of the piston?

Thanks for the ideas: - I’ll double check (what’s left) of the pistons for sizing to check clearance. - On the oil starvation suggestion, is there a likely culprit for cylinder 3&4 (right side of engine facing forwards)? Is there an oil passage that serves this side that could get blocked? The...

Hi all, I rebuilt my ‘79 CB750 and have been chasing low compression in cylinders 3&4. I pulled the engine and discovered catastrophic gouging to pistons 3&4 and the corresponding cylinder walls. All the piston rings are intact. Anyone have any idea what might have caused this...

Man, carbs are a pain. I’m still chasing down issues. If it helps I had plastic non adjustable ones and replaced them with adjustable black ones with metal tangs. I got them from David Silver Spares or CMSNL - not cheap but do help. Good luck with them.

Hi all, I’ve been working on my 1980 CB900 restoration. I have a generator cover from an engine (SC01) and another spare one from another engine (RC01). They are almost identical but some subtle differences in the inside ridge - one is more hollow and the other is filled in. My question is...

Cheers, the bowl was full when I pulled it but just checked the height and it was way too high compared to the others. I’m just working on it now and will update.

Hi, I did a complete require on my 1979 CB750 - I watched a lot of YouTube and found Brick House Builds does some excellent tutorial videos using a similar unit. This is a good starting point but there are another couple of good videos that he does.

have you had it running at all??

Hi, chasing down a carb issue (ok a few carb issues). I’ve done the see through tube float test and no one carb has zero fuel coming out the tube. I’ve pulled the carbs and no 1 does have fuel in the bowl. Float needle is free, jets are clean. Float height is as the other carbs. Anyone got...

Fantastic update!! Congratulations (!?!) on the 10 year anniversary!!!

I’ve done a bit of digging myself and I might have answered my own question - it looks like a Honda CBX 400 or 500 front faring frame/attachment.

Hi all, can you name the part? It came with my 1980 CB and I can’t figure out what it is. Thanks, Andrew

I changed the pegs for after market ones. Don’t think they lowered them that much.

Hi, good questions to my many questions: - temp taken using infrared thermometer - spark condition looks ok (each plug has spark) - timing - good question. I couldn’t figure out how to check the timing on the ‘79. - when it starts it is fine - no smoke from the pipes

I’m running Continental TKC 80 Twinduro…60% off, 40% on.

I’ll give that a shot.

Judicious use of black cable ties!!

Original tank…seat made by my wife from scratch.

Thats going to be a fun bike. Can’t say I love a bobber but I did cafe my 1979 CB750.

Hi, by way of follow up. I got all of mine out using the threaded rod, washer and nut method. One was worse than the other and I used a staple remover on the rod to give me extra purchase. It ended up coming out ok. Photos in case it is helpful to anyone.

Hi all, I’m having difficulties getting my 1979 CB750 firing on all cylinders - cold pipes on 1,2 and 3 and hot on 4. I have been working on diagnosing the issues and I feel like I’m getting nowhere fast. Any insight, ideas or wisdom out there?? Context and problems: - I’ve done a full top...